1. Field of the Invention
This invention relates to an adjustable hydraulic vibration damper for motor vehicles. The vibration damper has a damping piston fastened to a piston rod, with the damping piston dividing the work cylinder into two chamber portions which are filled with damping fluid. The damping fluid is able to flow between the two chamber portions along a connecting passageway. There is also at least one damping valve which reacts as a function of pressure to control the channel. This damping valve is controlled by a control body, and the control body is pressurized by a control pressure.
2. Background of the Invention
Damping force regulating devices for telescoping vibration dampers are known. For example, German Published Patent Application No. 33 03 293 discloses a damping force regulating device in which there is an additional, double-acting damping valve that is integrated into the damping piston itself. These double-acting damping valves are connected in series and can be separated from one another by a rotary disk valve. Such a configuration provides, in a first switching position, that only the valves of the guide piston carry a flow to thereby achieve a soft damping characteristic. In addition, in a second switching position, the valves in the guide piston and the supplemental valves carry an equal flow, so that a correspondingly hard damping characteristic can be set. To make any adjustments, a rotary disk valve is used, and this rotary disk valve is activated by an electrically operated actuator motor or servo-motor.
Other types of damping force regulating devices include adjustable vibration dampers. For example, German Patent No. 35 18 327 discloses a coil spring within the upper part of the piston rod of the adjustable vibration damper. Within this coil, an armature is axially movable as a function of the current fed to the coil. This armature creates a bypass opening between the upper and lower work chambers. Vibration dampers having such a magnetic coil, such as the damper disclosed in German Patent No. 35 18 327, are complex and expensive to manufacture.